I' working on a liting system which is using a T10 style of bulbs. They are 70 volts, 3 watts. There are 6 12 volt batteries to supply 72 volts. When the batteries are fully charged the voltage is approximately 78 volts and the bulbs are burning out. I'm thinking of installing resistors in the circuit to lower the voltage to 68 volts. Can someone tell me what size of resistor I would need and also should I drop the voltage lower to compensate for when the voltage is at 78?

  • \$\begingroup\$ Just for curiosity: What bulbs run on 70V? \$\endgroup\$
    – sgt_johnny
    Apr 14 '20 at 8:16

A dropping resistor in series with each bulb, to avoid filament burn-out with a fully charged battery, would entail power loss in the resistors and reduction of luminance at bulb voltage less than 70V.

Should a loss of luminance be acceptable, a better solution would be to use only five batteries (65V at full charge). The benefits would be zero power loss from dropping resistors and savings that would accrue by the elimination of one battery.

  • \$\begingroup\$ This is for an E-Bike. The previous versions where 60 Volts. They raised the voltage without upgrading the rear tail light bulbs. Running Stop And turn signals.I'm searching for LED replacement bulbs but the higher voltage ones. \$\endgroup\$
    – Claude d.
    Apr 14 '20 at 13:03
  • \$\begingroup\$ @Claude d., I got it! \$\endgroup\$
    – vu2nan
    Apr 14 '20 at 13:41

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